Universal Audio Attenuators-2 Channel

The RDL STP-1 is a two-channel universal audio attenuator designed to provide precise level control between audio sources and receiving equipment. It combines two adjustable attenuators in one passive package, giving installers a direct way to reduce incoming levels, preset operating points, match levels between devices, or increase audio input headroom. Because the circuit is passive, the STP-1 does not require an external power source.

Ideal Use Cases

The STP-1 fits audio paths where source output and equipment input levels require deliberate alignment. It can adjust audio entering equipment, establish preset audio levels, and precisely match levels across connected components. It is also suited to installations where attenuation is used to increase available input headroom. Its stated reference ranges cover line levels from +10 dBu to -10 dBu and microphone levels from -45 dBu to -65 dBu, supporting multiple signal-level contexts.

Why Choose This Model

Instead of requiring separate packages for two audio paths, the STP-1 provides two adjustable attenuators in one unit. Each channel uses a screwdriver trimming adjustment with 15 turns of continuous travel, allowing audio levels to be set with precision. The passive modified H and T pad circuitry accommodates HI-Z and LO-Z applications, with a nominal impedance of 10 kΩ for HI-Z operation and 600 Ω for LO-Z operation.

Installation and Integration

Audio connections are made through a terminal block that accepts 14 to 24 gauge wire. No wire lugs are required, simplifying direct termination at the unit. An input and output connection legend is located on the STP-1 to assist with correct wiring during installation. Since power is not required, integration does not call for a power outlet, external adapter, or additional power wiring. Adjustment is completed with a screwdriver at the 15-turn trimming controls after the audio paths are connected.

The specified ambient operating range is 20°C to 60°C. The product ships in a cardboard box measuring 2 x 2 x 4 inches, with a shipping weight of 0.19 pounds. The listed WEEE weight is 0.14 pounds.

Performance Highlights

The STP-1 supports several line configurations and specifies the maximum level for each. On a HI-Z balanced line, the stated level is +33 dBu or 35 V rms. On a LO-Z balanced line, it is +27 dBu or 18 V rms. For a HI-Z unbalanced line, the specified level is +35 dBV or 45 V rms. These ratings provide concrete guidance when selecting the appropriate impedance and wiring arrangement for the connected audio equipment.

The 15-turn continuous adjustment gives the installer a broad physical control range for precise trimming, while the passive circuit keeps the signal-level function independent of a power supply. Together, these characteristics make the unit suitable for fixed level-setting applications where settings are established during system integration.

What Makes It Different

The defining combination is two-channel attenuation, dual HI-Z and LO-Z impedance support, and passive operation within a single package. The STP-1 is not limited to one stated balanced-line configuration: it provides ratings for HI-Z balanced, LO-Z balanced, and HI-Z unbalanced operation. Its terminal block supports a practical 14 to 24 gauge wire range, while the printed connection legend and no-lug termination approach support straightforward integration.

Final Assessment

The RDL STP-1 is a focused solution for attenuating, presetting, and matching audio levels across two channels. Its 15-turn screwdriver adjustments, passive modified H and T pad circuitry, 10 kΩ HI-Z and 600 Ω LO-Z nominal impedances, and clearly specified line ratings give system installers the information needed to apply it accurately. For installations that need two adjustable attenuators without a power requirement, the STP-1 provides a direct and technically defined option.